
``Bastion`` --- Restricting access to objects
*********************************************

Deprecated since version 2.6: The ``Bastion`` module has been removed
in Python 3.

Changed in version 2.3: Disabled module.

Note: The documentation has been left in place to help in reading old code
  that uses the module.

According to the dictionary, a bastion is "a fortified area or
position", or "something that is considered a stronghold."  It's a
suitable name for this module, which provides a way to forbid access
to certain attributes of an object.  It must always be used with the
``rexec`` module, in order to allow restricted-mode programs access to
certain safe attributes of an object, while denying access to other,
unsafe attributes.

Bastion.Bastion(object[, filter[, name[, class]]])

   Protect the object *object*, returning a bastion for the object.
   Any attempt to access one of the object's attributes will have to
   be approved by the *filter* function; if the access is denied an
   ``AttributeError`` exception will be raised.

   If present, *filter* must be a function that accepts a string
   containing an attribute name, and returns true if access to that
   attribute will be permitted; if *filter* returns false, the access
   is denied.  The default filter denies access to any function
   beginning with an underscore (``'_'``).  The bastion's string
   representation will be ``<Bastion for name>`` if a value for *name*
   is provided; otherwise, ``repr(object)`` will be used.

   *class*, if present, should be a subclass of ``BastionClass``;  see
   the code in ``bastion.py`` for the details.  Overriding the default
   ``BastionClass`` will rarely be required.

class class Bastion.BastionClass(getfunc, name)

   Class which actually implements bastion objects.  This is the
   default class used by ``Bastion()``.  The *getfunc* parameter is a
   function which returns the value of an attribute which should be
   exposed to the restricted execution environment when called with
   the name of the attribute as the only parameter. *name* is used to
   construct the ``repr()`` of the ``BastionClass`` instance.
